Technical Field
This invention relates to new lubricating oil additives and lubricating oil compositions comprising the new lubricating oil additives. More specifically, it relates to passenger car engines and heavy duty diesel engines having lubricating oil compositions containing a friction reducing component comprising a salicylate compound that is molybdated with a bis-alkoxy alkyl/alkenyl amide/amine.
Description of the Related Art
While motor vehicle manufacturers continue to seek improved fuel economy through engine design, new approaches in formulating engine oils have played an important role in improving fuel economy and have resulted in improved emission characteristics of motor vehicles. Lubricant optimization is especially preferred over engine hardware changes, due to its comparative lower cost per unit in fuel efficiency and possibility for backward compatibility with older engines. Therefore, formulators are under continued pressure to develop engine oils and additive packages which take advantage of new performance basestocks and additive blends which demonstrate better fuel efficiency, oxidative stability, volatility, and improved viscosity index (to name a few characteristics) over conventional formulations. To improve fuel efficiency, there has been a drive to use lower viscosity engine oils, which often requires new additive package formulations. High on the list of requirements for these new formulated engine oil specifications are those employing components which improve the frictional properties of the lubricating oil composition. In this case, the additive system design is the crucial factor and close attention must be focused on the additive/additive and additive/base fluid interactions.
Engine oil acts as a lubricant between moving engine parts at various conditions of load, speed and temperature. Hence, the various engine components experience different combinations of boundary layer, mixed and (elasto) hydrodynamic regimes of lubrication. The largest frictional losses are at piston liner/piston ring interface, and a smaller part by the bearing and valve train. To reduce the energy losses due to friction of the various parts and to prevent engine wear, additives are incorporated into the engine oil such as friction modifiers, anti-wear agents, and antioxidants. The latter tends to lengthen the effect of the afore mentioned additives. Also, to reduce the hydrodynamic friction in the piston/cylinder, the viscosity of engine oils has been lowered. This has increased the dependence on friction modifiers to offset the new boundary layer regime. Hence, a vast amount of effort has focused on the interaction of oil viscosity with various friction modifiers to improve fuel economy.
Friction modifiers have been around for several years for application in limited slip gear oils, automatic transmission fluids, slideway lubricants and multipurpose tractor fluids. With the desire for increased fuel economy, friction modifiers have been added to automotive crankcase lubricants and several are known in the art. They generally operate at boundary layer conditions at temperatures where anti-wear and extreme pressure additives are not yet reactive by forming thin mono-molecular layers of physically adsorbed polar oil-soluble products or reaction layers which exhibit a significantly lower friction compared to typical anti-wear or extreme pressure agents. However, under more severe conditions and in mixed lubrication regime these friction modifiers are added with an anti-wear or extreme pressure agent. The most common type is a zinc dithiophosphate (ZnDTP or ZDDP), which, due to emissions considerations, has been reduced in concentration in many current formulations.
Molybdenum is a multifunctional additive that can act as an antioxidant, anti-wear, and friction modifier in lubricant oils. To incorporate molybdenum metal in oil soluble form has always been a challenge for additive chemists. The desire is to obtain a molybdenum containing compound with high molybdenum content and low viscosity so that it is easy to blend. Typical organo-molybdenum compounds include molybdenum dithiocarbamates (MoDTC), molybdenum dithiophosphates (MoDTP), molybdenum amines, molybdenum alcoholates, and molybdenum alcohol-amides.
Japanese Patent Application Number 2009227919 discloses a lubricant composition containing a reaction product of higher carboxylic acid diethanol amine and molybdenum oxide, and reaction product of higher carboxylic acid monoglycerol ester and molybdenum oxide, fatty amine compound and ester compound.
U.S. Pat. No. 4,647,388 discloses a lubricant additive that is the reaction product of a salt of a tertiary amine which has polyethylene oxide residues and ammonium molybdate and/or MoO3.
U.S. Pat. No. 4,889,647 discloses Mo complexes prepared by reacting fatty oil with diethanolamine (DEA) and a molybdenum source.
Chinese Patent Application Number 102533362, teaches an antioxidant containing an alkanolamide and molybdenum source.
U.S. Patent Application Number 20070073073 discloses a process for preparation of 2,4-heteroatom-substituted molybdena-3,3-dioxocycloalkane compounds.